RiRina, a girl living on an island,
takes a deep dive to discover a load of black pearls
inside a sunken ship.
After initial elation and excitement, she finds herself
out of breath and almost drowned to death.

The people who saved Rina from drowning
were a mysterious maritime species, called Mermaids.
Ever after, Rina covets to go to their realm, the Mermaid Kingdom.

Together with the strange turtle she had found on the coast,
Rina ventures into sunken vessels and underwater caves
in search of the people to whom she owes her life.
She struggles,
trying to go beyond her human freediving capacities.

Will Rina ever succeed in her probe?
What is the Test, that the Mermaids put upon her?

...Illustrations below
show Rina in her initial discovery of the black pearls.